FISHERY BULLETIN: VOL. 86, NO. 1 



catches in 1973 resulted from apparently ex- 

 tremely good survival and recruitment of individ- 

 uals spawned during the warm 1968-69 period 

 (Serra"^). Similarly, good survival of the large 

 1972 El Nino spawn could explain the huge catch 

 increases in 1976 and later years (Fig. 4). How- 

 ever, mean biomass estimates of age groups con- 

 tributing to the Chilean fisheries catch from 1974 

 to 1981 (Serra 1983) indicate increasing contribu- 

 tions after the 1967 year class with marked in- 

 creases beginning with the 1970 year class; this 

 suggests that factors other than temperature 

 (e.g., environmental change starting in 1969-70) 

 may also be responsible for increased larval sur- 

 vival and recruitment. A possible cause is in- 

 creased nearshore influence of equatorial and 

 subtropical waters (Santander and Flores 1983). 

 Because the sardine abundance increase was ini- 

 tiated prior to the 1972 anchoveta decline off 

 northern Chile (Fig. 4), it is difficult to implicate 

 reduced anchoveta competition as the cause of the 

 early sardine population growth in this area. 



The grouping of anchoveta with three coastal 

 species (Group I), and significant correlation of 

 anchoveta and Normanichthys crockeri larval 

 abundances are extremely interesting and imply 

 that the spawning intensity and/or early stage 

 survival of these four species are influenced in 

 similar ways by interannual changes off northern 

 Chile. Unfortunately, little is known about the 

 natural histories or population abundances of the 

 coastal species. Because of the group composition, 

 it is logical to suspect that coastal processes are 

 important factors influencing their larval abun- 

 dance. The significant negative correlation of the 

 group as a whole, and of two of the coastal species, 

 with ranked temperature and salinity values 

 (Table 10), suggests that coastal upwelling and/or 

 increased coastal influence by subantarctic 

 waters, and theoretically enhanced food supplies, 

 are important factors. 



Given the present data set and information 

 from recent publications, a case can be made for a 

 low-frequency environmental change influencing 

 the abundances of anchoveta and sardine larvae 

 as well as the larvae of coastal and mesopelagic 

 species during the 1964-84 period. The Chilean 

 OL composition suggests an environmental 

 change (e.g., an atmospherically related oceanic 

 circulation change) starting with the 1968-69 

 warm-water event. This coincided with apparent 



successful survival of sardine larvae and 

 markedly increased recruitment by 1968 and 

 later year classes despite varied warm water-cold 

 water events between 1968 and 1973. Physiologi- 

 cal anomalies of Peruvian anchoveta stocks in 

 1971 suggest that these fishes may have experi- 

 enced environmental change at that time. Unusu- 

 ally low proportions (e.g., 40% vs. typically 90%) 

 of potential spawning-sized fish were sexually 

 mature during the 1971 spawning season and fat 

 content of the 1971-72 catch was anomolously 

 high, indicating unusually low transfer of body 

 fat to gonadal products (Sharp 1980). Starting 

 with the 1972 El Nino was 1) an obvious in- 

 creased incidence of penetration of subtropical 

 surface waters toward the Peruvian coast, 2) co- 

 incidental onshore and southward expansion of 

 sardine spawning activity off both Peru and 

 Chile, 3) southward expansion of Peruvian an- 

 choveta spawning activity into new spawning 

 areas between 14°S and 18°S (e.g., to northern 

 Chile), and 4) a succession of years of poor an- 

 choveta larval survival off Peru and Chile (San- 

 tander and Flores 1983; Serra 1983). Environ- 

 mental conditions favorable for growth of sardine 

 populations, as well as of mackerel and jack 

 mackerel populations, off both Chile and Peru 

 have persisted since the early to mid-1970's (San- 

 tander and Flores 1983; Serra 1983). 



The lack of Chilean ichthyoplankton data from 

 the 1974-82 period precludes evaluation of the 

 constancy of altered species composition during 

 that time. However, there are indications that 

 change is once more occurring off northern Chile. 

 Preliminary analysis of ichthyoplankton samples 

 collected between Arica and Antofagasta during 

 4-14 August 1985 indicates a clear dominance by 

 anchoveta larvae at a markedly higher mean 

 abundance level than encountered in the 1964- 

 83 samples; sardine and Trachurus larval abun- 

 dances are comparable to those in the 1973 sam- 

 ples (Table 14). The other species have not yet 

 been analyzed, but Normanichthys crockeri is 



Table 14. — Mean abundance estimates and standard errors (num- 

 bers per 10 m2) and percent frequency of occurrence (F) of PL 

 taxa, OL and total larvae collected in 81 1 00-0 m WP2 net samples 

 off northiern Chile (18°-24°S) during 4-24 August 1985. 



Species 



(SE) 



(F) 



3Serra, R. Unpubl. manuscr. Subsecretaria de Pesca, 

 Teatinos 120, Piso 11, Of. 44, Santiago, Chile. 



Engraulls ringens 5,535.3 (1,844.1) (90.4) 



Sardinops sagax 63.8 ( 24.9) (26.6) 



Trachurus murphyi 1.2 ( 0.9) (2.1) 



Otfier species 233.7 ( 28.4) (92.5) 



Total 5,834.0 (1,838.2) 



22 



